Three-Dimensional Hierarchical Plasmonic–Semiconductor Heterostructure for High-Performance SALDI-MS Detection

Abstract Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is a powerful technique for small-molecule analysis but is often limited by inefficient laser-energy utilization and weak interfacial interactions. Herein, we report a three-dimensional hierarchical plasmonic–semiconductor heterostructure that enables the efficient capture, localization, and conversion of laser energy, thereby enhancing laser desorption/ionization efficiency. Vertically aligned CuO nanorods provide a high-surface-area photothermal architecture, while discretely distributed Ag nanoparticles generate localized electromagnetic hotspots, form Ag/CuO Schottky interfaces, and increase nanoscale roughness. Photothermal measurements, transient photovoltage analysis, finite-difference time-domain simulations, photoluminescence spectroscopy, and density functional theory calculations reveal a synergistic enhancement mechanism. Enhanced photon harvesting and plasmonic electromagnetic confinement promote nonradiative energy conversion, generating a transient thermal field that drives analyte desorption. Ion formation is likely facilitated by surface-assisted protonation/deprotonation processes and possible interfacial charge-transfer processes associated with charge separation at the Ag/CuO interface. Roughness-induced hydrophobicity and moderately strengthened analyte–substrate interactions further facilitate analyte enrichment while maintaining efficient desorption. As a result, the developed substrate exhibits a wide linear dynamic range (10–7–10–3 M, R2 > 0.99) and low detection limits of 0.4–0.8 nM for carbendazim, imidacloprid, and thiabendazole. It also demonstrates high reproducibility, spatial uniformity, and long-term stability. Reliable quantitative analysis is achieved in complex matrices, with results consistent with those obtained by UV–vis spectroscopy, demonstrating its potential for rapid and sensitive pesticide detection. This work provides a rational design strategy for high-performance plasmonic–semiconductor SALDI-MS substrates by integrating efficient laser-energy utilization and controlled interfacial carrier dynamics.